This invention relates to a method of communicating emergency warnings utilizing an existing cellular communication network, and a system for communicating such emergency warnings.
There are a number of situations where it is desirable to issue warnings to a broad audience in a selected geographic area. For example, in the case of severe weather, such as a tornado, it is desirable to warn persons in the areas affected so that they can seek shelter. In some areas, audible alarm systems are provided to warn residents of such weather emergencies. However, not everyone in the area can hear these warnings. Moreover, it is expensive to establish and maintain this elaborate system just for occasional use. Another example of a situation where it is desirable to issue an emergency warning to a broad audience in a selected geographic area is in the case of a nuclear power plant or a toxic waste handing site. In these situations, special radio receivers have been provided to persons in areas likely to be affected, and special transmitters provided to transmit warnings to those special receivers. Again, it is expensive to establish and maintain this type of elaborate system just for occasional use. Moreover, these systems are local by nature, and do not provide warnings to persons just passing through the area.
The present invention provides a method and system for communicating emergency warnings through an existing cellular communication network. Cellular communication networks, and in particular cellular telephone networks, now cover large portions of the United States. These networks comprise a plurality signal transmission stations distributed across a geographic region. The primary function of these networks is to facilitate communication by cellular telephones, and the systems are maintained for that purpose. Thus, the cost of establishing and maintaining a major portion of the system is already financed. The method of the present invention utilizes this established cellular communication network to communicate emergency warnings to a selected geographic area within the geographic region served by the network. According to this method, persons within the area are provided with warning devices that generate an emergency warning in response to a predetermined signal transmitted from one of the signal transmission stations in the cellular communication network. When an emergency situation occurs, at least one signal transmission station in the cellular communication network, appropriate to transmit the predetermined signal to warning devices in the affected geographic area, is selected. Then the predetermined signal is transmitted from the selected transmission station to cause warning devices in the selected geographic area to generate emergency warnings.
The emergency warning is thus selectively transmitted to those warning devices within a certain proximity of the selected transmission stations. By utilizing a preexisting cellular communication network, the only additional cost of implementing the method and system is the provision of warning devices, which can be relatively simple and inexpensive. By making these devices universal (which is only possible by using selected transmission stations), the cost can be reduced and the method and system can function to provide emergency warnings to persons merely passing through the geographic area affected by the emergency.
The method and system of the present invention improve the ability of emergency management agencies to reach the population. The method and system operate independently of regular telephone and electrical service, which can be compromised in emergency situations. The method and system reaches persons inside buildings where sirens might be difficult to hear and where televisions and radios may not be in operation.
The system is simple in construction and operation. The warning units are triggered by a common predetermined signal, and geographical selectivity is achieved by proximity to particular cellular transmission stations. This eliminates the need for geographic encoding of the warning devices, or programming units for specific locations.